4D Digital Subtracted Angiography (DSA) is a sequence of reconstructed 3D angiography images over time, representing blood flow information, typically within the head. The subtraction of the flow image from a baseline image removes the static anatomy such as the skull, leaving only the flow information. In conventional systems, due to scanner limitations, the 3D volume of each 4D DSA time step is reconstructed from a limited number of scanner images projected from a narrow range of projection angles. On these images, multiple vessel branches at different depth might be projected onto the same region. The overlapping vessel branches result in reconstruction artifacts (e.g., blood flowing from minor branches to a major artery). Accordingly, it is desired to provide a technique for reducing these artifacts to produce a higher-quality image.